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Penicillin ‘Allergy’ Label at Hospital Admission May Lead to 10% Longer Hospital Stays

But less than 5% of patients with history of ‘allergy’ are truly allergic

A new study in the Journal of Allergy and Clinical Immunology finds that a penicillin “allergy” label adversely affects the quantity and quality of health care in hospitalized patients. According to the report, the penicillin allergy label is the most common drug allergy listed in medical records during hospital admissions.

The study looked at the records of more than 51,000 patients admitted to Kaiser Foundation hospitals in Southern California over a 3-year period (2010–2012). The study found that about 11% of these patients carried a penicillin “allergy” label.

“It is important to know if you are allergic to penicillin,” said Eric Macy, MD. “This medical-history detail impacts not only critical health-care decisions, but it greatly impacts cost. In the hospital setting, we found this translates to about 10% more hospital days and significantly more Clostridium difficile, methicillin-resistant Staphylococcus aureus [MRSA], and vancomycin-resistant enterococcus [VRE] infections. These adverse events occur because penicillin ‘allergic’ patients are given more broad-spectrum antibiotics, including ciprofloxacin, vancomycin, clindamycin, and third or greater generation cephalosporins. Previous work by our group has shown that less than 5% of individuals who carry a history of penicillin allergy are truly allergic.”

A penicillin allergy history, although often inaccurate, is not a benign finding at hospital admission, the study says. Subjects with a penicillin allergy history spend significantly more time in the hospital. These subjects are also exposed to greater risk of infection and significantly more antibiotics previously associated with C. difficile and VRE.

It has been estimated that of the 30 million U.S. patients reporting as penicillin allergic, 28.5 million are not. That means that up to 19 out of 20 patients who think they are allergic to penicillin are misinformed, Macy commented. This over-reporting of penicillin allergy may lead to higher medical costs for both patients and the health care systems. Antibiotic costs for patients reporting penicillin allergies are up to 63% higher.

In addition to cost savings, testing for a penicillin allergy may be important because it improves patient care and combats drug-resistant bacteria, the study notes.

Currently, Pre-Pen (benzylpenicilloyl polylysine injection USP, ALK-Abelló, Inc.) is the only FDA-approved skin test for the diagnosis of penicillin allergy. It is indicated for the assessment of sensitization to penicillin (benzylpenicillin or penicillin G) in patients suspected to have clinical penicillin hypersensitivity. A negative skin test to Pre-Pen is associated with an incidence of immediate allergic reactions of less than 5% after the administration of therapeutic penicillin, whereas the incidence may be more than 50% in a history-positive patient with a positive skin test to Pre-Pen.

These allergic reactions are predominantly dermatologic. Whether a negative skin test to Pre-Pen predicts a lower risk of anaphylaxis is not established. Similarly, when deciding the risk of proposed penicillin treatment, there are not enough data to permit relative weighing in individual cases of a history of clinical penicillin hypersensitivity compared with positive skin tests to Pre-Pen and/or minor penicillin determinants.

Sources: PR Newswire; March 10, 2014; JACI; March 2014; and Pre-Pen Package Insert; October 2009.

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